Ray's Sudoku

Large Size

Java Runtime Environment 5.0 Update 6.

The Rules

The rules of Sudoku are simple: Enter values (from 123456789ABCDEFG depending on puzzle size) in the square cells such that every cell in every row, column and box has a distinct value. The valid symbols vary with the puzzle size. If the size is 9, the symbols are 123456789. For size 4, the symbols are 1234. For size 12, they are 123456789ABC, etc.

Solving the Puzzle

After creating a puzzle "Play" mode is selected so you can solve the puzzle. Simply enter symbols following the rules above until it is completed. A timer is provided to record the elapsed time in play mode. You will notice that the puzzle is blanked under certain conditions showing a "Click to Continue" message. This indicates that the clock is stopped. When you click on the blank puzzle, the board will reappear and the clock will resume. The clock is stopped whenever you shift your attention away from the puzzle by, for example, clicking on another application.

Pencil Color

You can use up to three colored pencils to fill in a puzzle. An eraser is supplied for selectively erasing each color. Use a different color when you are uncertain that you are filling in correct symbols. If you later discover that your uncertainty was well-founded (you encounter contradictory constraints), you can erase some all of the symbols with that color.


Every empty cell has spaces into which you can enter notes to yourself to help solve the puzzle. You might, for example, note the symbols that are allowed in the cell. The amount of space is limited to the number of symbols in the puzzle (e.g. nine for the standard puzzle size).


Hints shows you the symbols that each cell is constrained to contain. This is definitely cheating. Symbols shown in gray are allowed because no other cell in any of the three constraint sets (row, column or box) has the symbol. If there is exactly one such symbol it is colored aqua instead of gray. Symbols shown in black are further constrained to be placed in a cell because there is no other cell in the row, column or box of the cell that is allowed to have the symbol.

Puzzle Creation

You must be in "Edit" or "Enter" mode to create a puzzle. Then use the "New" button to create a new puzzle to solve. Large puzzle sizes take much longer to generate; be prepared to wait. If you are a newbie, use a small puzzle size until you get the hang of it.

In addition to puzzle size, there are factors that, generally, increase the difficulty of a puzzle. These factors may be individually enabled to make the puzzles harder. The factors are related to the degree of redundancy in the puzzle; more redundant puzzles are easier since there are usually more places where the correct symbol is evident.

Each created puzzle has an id that can be used to regenerate the same puzzle at a later time. Use this if you encounter an interesting puzzle that you wish to share with your friends. Enter the puzzle id into the new puzzle dialog exactly as it appears in the puzzle id field and click "Build".

You can also generate puzzles manually. Select "Input" mode if you simply want to copy a puzzle from another source such as a newspaper. Select "Edit" mode and enable "Hints" to see values that are directly allowed by the values in the other cells. Values that are forced (cells having only one allowed value) are automatically filled as if played (colored black). These cells are not part of the initial board.

With larger size puzzles, it becomes likely that entered symbols may make it impossible to fill some other sets (box, row or column). When this happens, the affected sets are marked with rose-colored X's. Enter a different value in one or more of the marked cells.

Cells are color coded as follows:

GreenAllInitial cell
AquaEditRedundant Initial cell (value is forced)
BlackEditShow plays that will be forced
BrownPlayA manually played symbol
Tan Play A manually played symbol
Gray Play A manually played symbol
RedEditA cell in conflict with another
Hints are also color coded as follows:
GrayAll Allowed symbol
BlackAll Forced by absence of any other allowed cell
Aqua All Forced by absence of any other allowed value